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Re: MS parabolics, dual omnis

Subject: Re: MS parabolics, dual omnis
From:
Date: Sat, 22 Mar 2003 18:07:09 EST
Walt wrote, about my mention of doing MS stereo with a fig8 mike behind the 
dish:

<< Why did you mount the fig 8 behind 
the dish instead of in front? >>

I was looking for separation and time coherency.  If I put the fig8 up in the 
dish, its view of the side-to-side world is masked by the dish, and the 
natural amplification of the dish would also tend to make the mid information 
overwhelm the sound from the sides in the fig8.  But by putting the fig8 
behind the dish, I could use the shadowing of the dish to give better 
isolation between mid and sides, while maintaining time coherence for any mid 
sound coming from the direction the dish pointed.  The fig8 was about as far 
behind the dish as the omni mid was in front of the dish.

When I first thought about doing this, I expected there to be a real sonic 
disconnect between the mid and sides images.  I was pleasantly surprised at 
the extent to which they integrated in stereo.

One caveat: this obviously works best when you can stand-mount the whole 
contraption and get your own breath and handling noise away from the fig8.

Greg Weddig wrote:
> For ambient soundfields a mono signal can be achieved simply by using
> only one channel.  Then you have no worries about phase cancellation.

We're always needing to evaluate how things sound in both stereo and mono.  
We release the Morning Edition program (where Radio Expeditions runs) in 
stereo.  But some public radio stations sum it to mono so they can run their 
transmitters in mono, and get a bit greater coverage area than they can 
cleanly get with stereo.  (They'll switch to stereo for music programs, but 
consider NPR news programs as "talk" programs.)

And even when the stations carry the show in stereo, many listener radios are 
mono (although fewer and fewer as the years go on). So we want to know that 
mono listeners will still have something interesting to listen to, while the 
stereo listeners get more thrills.

As for comments about dual omni recordings not having a solid center image: 
sometimes that's bad, sometimes it's good for us.  If we're looking for an 
ambience recording that can stand on its own for a while, then a coherent 
center is a good thing.  If we're looking for a background ambience to use 
behind voice-over narration, then a hole in the middle of the stereo field is 
a great place to put the narrator! Typically such recordings will sound 
quieter in mono, but in noise-compromised listening situations like cars we 
want to make sure the ambi doesn't overwhelm the narrator.

--Flawn Williams




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